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Old Aug 31, 2010, 07:30 PM
Heli's rule!
dacaur's Avatar
Midvale, Utah, USA
Joined Mar 2005
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Quote:
Originally Posted by rsobel View Post
I've been trying to play more with my DX6i settings. I'm really good with math and excel. Does anyone know the formula or how I can do something in excel so I can compare the graphs of, for example, DR/EXPO of 80% rate with -50% expo to say 100% rate with -30% expo. How can I plot these? Anyone know the equations? Thanks
I doubt anyone does... how exactly would this be useful? Even if someone had taken the time for god knows why to plot it, I doubt it would be the same from MFG to MFG.....
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Old Aug 31, 2010, 07:54 PM
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United States, SC, Charleston
Joined Feb 2010
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Well, for what I'm trying to do, it would help me compare the slope at different points along the two curves (e.g., would the stick be more or less sensitive at half stick). I think this is a standard formula, something along the lines of y = a * x * exp(-r) or something, where the a has something to do with the dual rate value and the r is the expo ... but this isn't it, I'm just hoping someone knows it
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Old Aug 31, 2010, 09:40 PM
high flyer
stalyoni's Avatar
Sydney, Australia
Joined May 2008
3,142 Posts
Ok so i have my SR 120 on the way in the mail.

What dx6i settings are you guys using? Should i just clone my MSR settings and modify them a little to suit this new heli?
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Old Aug 31, 2010, 09:59 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
24,765 Posts
[QUOTE=stalyoni;15931391.. sleepy and precious are both out of action for now...[/QUOTE]

Uh-oh...

Do you bust them again..?

BJ
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Old Aug 31, 2010, 10:01 PM
The lunatic is on the grass
ridgewalker's Avatar
Joined Aug 2008
4,915 Posts
Thats what i did stalyoni.
The msr settings worked great.I imedietly switched the links on the swash to the longer balls.It will give you better control,and you can use the gyro sw to toggle between high and low rate to take the edge off when you want to.
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Old Aug 31, 2010, 10:02 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
24,765 Posts
Quote:
Originally Posted by stalyoni View Post
yah its all good dooms day, sometimes i take things the wrong way

OK so i finally made a deal with the guy. $195AUD posted, comes with 2 lipos, spare blades, TX (which i don't need), wall charger and all the normal stuff that comes with it. I cant wait now.

BJ all i have to do is think of a name for it now.....Any suggestions?

Still havent got one for my MCX ether......Hmmm
You could also call it *ahem*...."BJ"

I honour of the b@stard that tipped you over the edge into buying one... lmao

BJ
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Old Aug 31, 2010, 10:02 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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Originally Posted by isogloss3d View Post
I like to unplug the main motor and wave the MSR around in my hand to hear the "mosquito" sing in harmony with the gyro. I wonder what key my blade 120 SR sings in? b flat? I'll have to try it and find out.
Eb-blunt ??

BJ
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Old Aug 31, 2010, 10:05 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
24,765 Posts
Quote:
Originally Posted by rsobel View Post
I've been trying to play more with my DX6i settings. I'm really good with math and excel. Does anyone know the formula or how I can do something in excel so I can compare the graphs of, for example, DR/EXPO of 80% rate with -50% expo to say 100% rate with -30% expo. How can I plot these? Anyone know the equations? Thanks
Are you trying to work out the theoritical maximum throw per notch of stick travel between the two rates?

BJ
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Old Aug 31, 2010, 10:07 PM
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United States, SC, Charleston
Joined Feb 2010
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no, just trying to figure out the trade-off between higher rate and less expo. In other words, by upping the rate from 80% to 100% at the same time as lowering the expo from -50 to -30, does that make it more or less sensitive (which is the slope) around center stick.
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Old Aug 31, 2010, 10:10 PM
high flyer
stalyoni's Avatar
Sydney, Australia
Joined May 2008
3,142 Posts
Quote:
Originally Posted by BJ64 View Post
Uh-oh...

Do you bust them again..?

BJ
yeh in the MSR loop and crash video. Smashed the canopy pegs off the frame. The skids where already busted when i flew it. The SR needs a new tail rotor. I still have the MCX and the CHAMP to fly, oh and the good ol' esky lama v4 (need to adjust the servo arms).

Anyways i gotta goto work now.
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Old Aug 31, 2010, 10:46 PM
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Charlotte Douglas, NC
Joined Sep 2003
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How about Grumpy for the name of the 120
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Old Aug 31, 2010, 10:55 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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Long Post

Quote:
Originally Posted by rsobel View Post
no, just trying to figure out the trade-off between higher rate and less expo. In other words, by upping the rate from 80% to 100% at the same time as lowering the expo from -50 to -30, does that make it more or less sensitive (which is the slope) around center stick.
My JR Tx shows me a graphic of that stick's response curve as I adjust the amount of expo.

I run +30% expo on 'low rates' for a lot of things - not -30%. Not sure what Tx you're running or how it deals with Expo - but generally speaking, going -ve Expo makes it more sensitive, not less.

I think you'll find that your 'travel' percentage is always going to be the same that you've set it to - no matter what Expo you're using. 80% throw will always be 80% throw from the Tx's point of view. Now, 80% on one Servo may be different compared to 80% on a different Servo hooked up to the same channel when it comes to finite distance travelled. Or, indeed, a different Tx/Rx hooked up to the same servo.

Having said that, 80% should more or less still be 80% - but that's why you have trims anyways.

Using 80% throw and +30% Expo as an example, the amount of Expo you run determines when and how fast you get to that 80%. Full-stick should always be 80%, but with +30% Expo your throw should react exponentially for about 30% of the stick movement (?), and then revert back to linear once the stick is outside that movement range. The more +ve Expo you dial in, the more of the stick movement either side of centre will be exponential i.e. moving the servo gradually at first as you the move stick away from centre until servo response becomes linear again once your stick position has crossed the threshold from expo servo response to linear servo response.

I can dial in different amounts of Expo for each direction away from centre-stick for that channel on my Tx.

I don't think it's an exact science that you can plot a set of curves for, say, 100% throw and +50% Expo on high rates, and 80% throw and +30% Expo on low rates that will work across all Models etc. The Servo's themselves have their own characteristics like torque/movement v's lag time etc.

But, for the one model, 100% throw and +50% Expo will mean that not much will happen for the first 50% of stick movement, then it will suddenly become linear and the Servo will move rapidly from where it currently is to 100% throw with the remaining 50% of stick movement (or thereabouts). So, it will respond rather 'spongy' around half-stick, then get rather lively for the rest of the stick movement = not much happening to a fairly nervous movement rather quickly.

At 80% throw and +30% Expo, the Servo (hence the control surface) will move slowly to around 30% of stick movement, and then be fairly crisp until the Servo reaches it's maximum extent which is now limited to 80% of what it could potentially reach.

In normal conditions, you don't really want too much Expo - that makes the Servo's non-responsive for a lot of the stick movement and then they suddenly go full-tilt to their maximum throw.

15-30% Expo helps n00bs like me by deadening the other channel on the same stick e.g. while I'm unintentionally giving a bit of Rudder while I'm operating the Elevator. Fat thumbs are a curse... LoL

BJ
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Old Aug 31, 2010, 10:56 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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Quote:
Originally Posted by DoomsDay View Post
How about Grumpy for the name of the 120
LoL

I think we have a hit!

BJ
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Old Aug 31, 2010, 10:57 PM
Heli's rule!
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Midvale, Utah, USA
Joined Mar 2005
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Quote:
Originally Posted by rsobel View Post
no, just trying to figure out the trade-off between higher rate and less expo. In other words, by upping the rate from 80% to 100% at the same time as lowering the expo from -50 to -30, does that make it more or less sensitive (which is the slope) around center stick.
I see what you are trying to do, though I still dont understand why.... You dont get a truly great flying model from a spreadsheet, you get it by experimenting with settings....

That said, honestly for a heli like this, if you have access to expo, you shouldn't be using dual rates at all. Dual rates ideally should only be used for something like a CP heli where you might sometimes want to fly around scale like and sometimes do 3D, or a plane where you use low rates for takeoff and landing and flying around, and then do stunts on high rates. Personally, I avoid ever using dual rates since I have access to expo on my DX7, Ive seen and heard of too many planes and heli's destroyed because the pilot forgot which rates they were on....

I think of dual rates as a "poor mans expo". If you dont have access to expo you can use dual rates to achieve the same thing, but its not as good, because you have to flip a switch. Using expo is like having dual rates where you dont have to flip a switch or remember if you are currently using high or low rates... Set your expo, If you find you are over controlling and wish for a "low rate", use less expo (assuming you are using neg expo, you could go from 50% to 30%)....
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Old Aug 31, 2010, 11:21 PM
Registered User
Joined Jan 2007
118 Posts
Hello:how are you guy's controlling this Blade 120SR? I have mine on a DX6I With the MSR Setup and it Seem's to hover ok,but try to move around and this thing is all over the place.Is it just me,or is this 120SR the worst heli I ever had? I go forward,try to turn,and it seems to go all over the place.I don't see where this heli is supposed to be a stable heli? What am I doing wrong? If anything.Getting really frustrated with this one.
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